[ncl-talk] Write grib2 to netcdf

[Dennis Shea]

If you want a time dimension

%> ncl_convert2nc  aod.2014100400.grb -itime

or, more elaborate, change NCL's dimension name

%> ncl_convert2nc aod.2014100400.grb -itime -u initial_time0_hours -U time

Ignore any warning message .. not important

%> ncdump -h aod.2014100400.nc


etcdf aod.2014100400 {
dimensions:
        time = UNLIMITED ; // (1 currently)
        lat_0 = 181 ;
        lon_0 = 360 ;
        ncl_strlen_0 = 18 ;
variables:
        float AOTK_P48_GLL0(time, lat_0, lon_0) ;
                AOTK_P48_GLL0:forecast_time_units = "hours" ;
                AOTK_P48_GLL0:forecast_time = 0 ;
                AOTK_P48_GLL0:parameter_template_discipline_category_number
= 48, 0, 20, 102 ;
                AOTK_P48_GLL0:parameter_discipline_and_category =
"Meteorological products, Atmospheric chemical constituents" ;
                AOTK_P48_GLL0:grid_type = "Latitude/longitude" ;
                AOTK_P48_GLL0:_FillValue = 1.e+20f ;
                AOTK_P48_GLL0:units = "Numeric" ;
                AOTK_P48_GLL0:long_name = "Aerosol optical thickness" ;
                AOTK_P48_GLL0:production_status = "Operational products" ;
                AOTK_P48_GLL0:center = "US National Weather Service - NCEP
(WMC)" ;
        double time(time) ;
                time:units = "hours since 1800-01-01 00:00" ;
                time:long_name = "initial time" ;
        double initial_time0_encoded(time) ;
                initial_time0_encoded:units = "yyyymmddhh.hh_frac" ;
                initial_time0_encoded:long_name = "initial time encoded as
double" ;
        float lat_0(lat_0) ;
                lat_0:La1 = 90.f ;
                lat_0:Lo1 = 0.f ;
                lat_0:La2 = -90.f ;
                lat_0:Lo2 = 359.f ;
                lat_0:Di = 1.f ;
                lat_0:Dj = 1.f ;
                lat_0:units = "degrees_north" ;
                lat_0:grid_type = "Latitude/Longitude" ;
                lat_0:long_name = "latitude" ;
        float lon_0(lon_0) ;
                lon_0:La1 = 90.f ;
                lon_0:Lo1 = 0.f ;
                lon_0:La2 = -90.f ;
                lon_0:Lo2 = 359.f ;
                lon_0:Di = 1.f ;
                lon_0:Dj = 1.f ;
                lon_0:units = "degrees_east" ;
                lon_0:grid_type = "Latitude/Longitude" ;
                lon_0:long_name = "longitude" ;
        char initial_time0(time, ncl_strlen_0) ;
                initial_time0:NCL_converted_from_type = "string" ;
                initial_time0:units = "mm/dd/yyyy (hh:mm)" ;
                initial_time0:long_name = "Initial time of first record" ;

// global attributes:
                :creation_date = "Wed Oct  8 13:35:24 MDT 2014" ;
                :NCL_Version = "6.2.0" ;
                :system = "Darwin sheamac.cgd.ucar.edu 13.4.0 Darwin Kernel
Version 13.4.0: Sun Aug 17 19:50:11 PDT 2014;
root:xnu-2422.115.4~1/RELEASE_X86_64 x86_64" ;
                :Conventions = "None" ;
                :grib_source = "aod.2014100400.grb" ;
                :title = "NCL: convert-GRIB-to-netCDF" ;

On Wed, Oct 8, 2014 at 12:41 PM, Partha Bhattacharjee <pbhatta2 at jhu.edu>
wrote:

>  ​Thanks Dave. It worked.
>
>
>  Partha
>  ------------------------------
> *From:* David Brown <dbrown at ucar.edu>
> *Sent:* Wednesday, October 8, 2014 2:29 PM
> *To:* Partha Bhattacharjee
> *Cc:* ncl-talk at ucar.edu
> *Subject:* Re: [ncl-talk] Write grib2 to netcdf
>
>  If you use ncl_filedump on your GRIB2 file you will see that it has no
> time dimension. There is only a lat and a lon dimension. The script you are
> using is trying to read a time dimension that does not exist -- therefore
> the error. The simplest and most general way to convert any GRIB file to
> NetCDF is to use the script ncl_convert2nc, which is supplied with every
> NCL installation. If the 'ncl' binary is in your PATH then ncl_convert2nc
> will be as well, assuming you have a standard installation.
>  -dave
>
>
>
> On Wed, Oct 8, 2014 at 10:41 AM, Partha Bhattacharjee <pbhatta2 at jhu.edu>
> wrote:
>
>>  ​Forgot to add information about my earlier question. I am using NCL
>> 6.2.1.
>>
>>
>>  Partha
>>  ------------------------------
>> *From:* ncl-talk-bounces at ucar.edu <ncl-talk-bounces at ucar.edu> on behalf
>> of Partha Bhattacharjee <pbhatta2 at jhu.edu>
>> *Sent:* Wednesday, October 8, 2014 11:39 AM
>> *To:* ncl-talk at ucar.edu
>> *Subject:* [ncl-talk] Write grib2 to netcdf
>>
>>
>> I was using slightly modified form of an example in NCL page
>> https://www.ncl.ucar.edu/Applications/gribeff.shtml to convert grib2
>> file to netcdf. However, ncl cannot read the time information from input
>> grib2 file and stops where "initial_time​" is mentioned. Grib2 file and ncl
>> code are attached. Any help is appreciated.
>>
>>
>>   Thanks.
>>
>>  Partha
>>
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>
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